Shoe stiffener and method of making same



May 19, 1953 G. E. EHLE SHOE STIFFENER AND METHOD OF MAKING SAME Filed June 26, 1948 me/wko@ GEORGE E EHLE www:

Patented May '19, 1953 Izssrzit SHOE STIFFENE NIAKIN George E. Ehle, Lanea R AND METHOD OF G SAME ster Township, Lancaster County, Pa., assignor to Armstrong Cork Company, Lancaster, Pa., a corporation of Penn- Sylvania Application June 26, 1948, Serial No. 35,453

6 Claims.

This invention relates to a shoe stilener and method of making the same and is concerned particularly with Water-soluble resin impregnated stiffeners such as those fabricated with a Watersoluble aminoplast impregnant.

It has been proposed in Almy Patent 2,277,941 to form a shoe stiffener by saturating a fibrous web such as double napped cotton flannel with a mixture of urea-formaldehyde resin and rubber latex carrying a porous filler such as diatomaceous earth. The saturated web is dried and then cut into stilener blanks such as box toes. The urea-formaldehyde resin is in a low stage ofcondensation and is Water-soluble. The resin is stabilized and is capable of being activated (converted to a hard, Water-insoluble condition) upon treatment With phosphoric acid or ammonium phosphate. Shoe stilfeners of this type are supplied to the shoe manufacturer as cut blanks in a dry, sti condition and are immersed in an activating solution at the shoe factory immediately prior to the insertion of the stiffener into the shoe. The solution renders the blank soft and flaccid so that proper lasting may be effected, and, since the solution contains an activator, the blank is rendered hard and waterinsoluble upon drying and setting.

It is desirable in shoe manufacture to use a stiffener which may be made soft and lastable in a relatively short period of time. Generally, the stiffener is dipped into the softening solution and is then withdrawn and permitted to mull t thus effect the desired softening of the blank for proper lasting in the shoe. With the urea-formaldehyde type of stiffener, using a diatomaceous earth filler, mulling requires in the order of 30 seconds to two minutes. The use of a diatomaceous earth ller in water-soluble resin impregnated stiffeners has a desirable effect upon the rate of mulling, for the diatomaceous earth is naturally porous and thus aids in getting moisture Within the blank and in contact with the resin, but the quantity of diatomaceous earth which can be incorporated is limited because of the shape and character of the particles; they have a great tendency to filter out on impregnation of the fabric foundation and thus do not properly penetrate throughout the thickness thereof. acteristic of the diatomaceous earth is its siliceous nature; it is extremely hard and tends to rapidly dull the knives employed in the skiving of the stilener blanks.

Another problem involved in the use of water- ,soluble resin impregnated stiieners is the sus- Another objectionable charf ceptibility of the stiffener to change upon the labsorption of moisture. 'The material has a tendency to absorb moisture from theA atmosphere, particularly during Warm, humid, summer days, and, since the sheet material must, in most instances, be skived subsequent to dieing out into the appropriate shape, the absorption of water by the blank rendersit sticky or tacky and very diflicult t0 skive.

There is also the problem of dehydration of the impregnant in the stiffener material under low humidity conditions, as in the Winter months, and this results in a reduction in solubility, lengthening the time'for softening. y

A further problem is encountered with the Water-soluble resin impregnants heretofore used and this is the tendency for liller particles to settle out in the impregnant, thus making it difcult to secure a uniform impregnation of the base or foundation fabric for the stffener, with the ller particles properly dispersed throughout the mixture.

Urea-formaldehyde resin saturants previously suggested possess substantially no natural porosity as finally dried, and softening is effected practically entirely by the solvent action of the Water n the activator upon the thin films of urea resin which surround the fibers and are disposed therebetween; this requires a substantial mulling period prior to lasting.

An object of my invention is to provide a Watersoluble resin impregnated shoe stiffener which may be softened and rendered flaccid substantially instantaneously upon immersion in a Water solution of an activator for the resin, requiring no mulling.

Another object of my invention is to provide a Water-soluble resin impregnated shoe stiffener which is resistant to the deleterious action induced by the `absorption of moisture from the atmosphere, and which will not excessively de` hydrate under 10W humidity conditions.

A further object of vmy invention is to provide a Water-soluble resin impregnated shoe stiener in which the resin is in a porous condition to facilitate softening.

An additional object of my invention is to provide a method of making shoe stiffener material which will be extremely porous, -the porosity at least in part resulting from fracture of the im pregnating resin after deposition and drying on the fibers of the supporting base of the stilfener.

In order to attain the foregoing objects, the impregnant is renderedk porous so that,'instead of the Water of the activating solution Working on continuous films of resin on the fibers of the base fabric, it Will act on discontinuous films which may be quickly penetrated throughout their extent. This porosity is preferably achieved by incorporating an agent into the resin solution which willcause it to dry `as a discontinuous, porous film.

Preferably, the material is also opened mechanically, and this may be accomplished by napthe dried resin on the fibers, and this is facilil tated, of course, by the napping of the resin impregnated fabric and drying in distended condition. This fracturing may be accomplished by passing the napped and dried resin impregnated fabric through va pair of relatively closely set calender rolls.

By rendering the resin impregnant porous, by mechanically opening the fibrous structure, and by fracturing the resin, the speed of softening is so increased that naturally porous fillers such as diatomaceous earth may be dispensed with, but, more important, this combination also renders it feasible to vincorporate large quantities of finely divided fillers which, when disposed througout the fabric, serve both to render the stiffener resistant to deleterious action from moisture absorbed from the atmosphere or lost to the atmosphere and to further enhance the speed of softening by increasing the surface area of the dried, porous resin available for Contact with the water of the yactivating solution, eliminating the necessity for mulling In order that the invention may be readily understood, a preferred embodiment thereof will be described in conjunction with the attached drawing in which the single View is a diagrammatic illustration of equipment useful in carrying out my process to which appropriate descriptive designations of the various parts have been applied.

In my preferred practice, rI prepare an impregnating bath by mixing together the following ingredients in .the proportions given, all parts being by weight:

150 urea-formaldehyde syrup (70% solidswater-soluble resin) 80 water 4 dispersing agent 100 ground screened talc I- 60% wetting agent (30% solution in solids water) latex (polychloroprene-50% solids) 10 thickener (15% solution in water) 5 glycerine While I prefer to use a urea-formaldehyde resin, other water-soluble aminoplast resins of a similar nature may be employed such as the thiourea aldehyde resin, urea aldehyde derivative type of resin, melamine aldehyde resin, or mixtures thereof. The urea-formaldehyde resin disclosed in Almy Patent 2,277,941 may be used with excellent results and is preferred.

A dispersing agent is included in the mixture to aid in the proper distribution of the various components of the mixture, particularly the iiller. Any of the well-known dispersing agents may be used, although I prefer to use the alkyl aryl sulfonate type.

The ground screened talc is a relatively soft llcr material and is preferably of a fineness of 300 mesh, U. S. standard, or finer.

In place of the tales, other acid resistant fillers such as micas, clays, or other inorganic materials of a similar nature may be substituted. Organic llers such as walnut shell our or insolubilized starch may also be used. These are all acid resistant llers in the sense that they are substantially inert toward the acid used in the conditioning solution such as a water solution of ammonium phosphate. The quantity of filler employed will vary but will generally be in the range between and 120% based upon the dry weight of the resin of the impregnant, being preferred.

The wetting agent is employed to facilitate the impregnation of the resin solution into the base fabric. I prefer to use one of the proprietary wetting agents of which many are currently available.

The latex serves a dual function; primarily, it adds adhesiveness to the impregnating mixture so that proper and effective bonding of the stiffener to the shoe parts may be obtained; and, incidentally, it serves as a plasticizer for the resin. I prefer to use a latex such as polychloroprene (neoprene).

In some stiieners,y the rubber latex may be eliminated, but, for most purposes, the incorporation of this material is desirable. In place of polychloroprene, other synthetic rubber latexes may be employed or natural rubber latex may be used. Synthetic resin plasticizers and adhesives may also be incorporated either alone or in substitution for a part of the natural or synthetic rubber latex. Preferably, the plasticizer is incorporated in an amount equal to about 10% to 20% of the weight of the resin.

The thickener is lpreferably' sodium polyacrylate, and it serves to increase what is generally termed the apparent viscosity of the impregnating composition for the purpose of facilitating the napping operation and rendering the dried impregnant porous, both of which will be more fully hereinafter described, while at the same time.

avoiding any substantial increase in the solids content of the impregnating solution. It also serves to maintain the ller particles in proper suspension in the impregnant, avoiding settling and segregation.

In place of the sodium polyacrylate, other thickeners such as carboxymethylcellulose, derivatives of poiyacrylic acids, bentonite, silica gel, gum arabic, or gum tragacanth may be employed. These are all gel type thickeners which are inert toward the other impregnating ingredients, particularly the resin constituent thereof.

The small quantity of glycerine employed serves to maintain a small but effective quantity of moisture in the finished material, particularly in winter weather when low humiditiesy are encountered. lOther humectants may be substituted for the glycerine.

In order to secure thevdesired physical characteristics and qualities in the lasted stiffener such as hardness, waterproofness, resilience, etc., and the optimum porosity and other qualities of the stiffener blank, the base fabric should preferably carry and have impregnated into it between 200% and 300% impregnant, based upon the dry weight of the base fabric and the dry weight of the impregnant. In the specific example given above where the base fabric is a cotton flannel weighing @Ai pound per square yard, the dry weight of the impregnant in and on the fabric should be between l and 11/2 pounds per square yard. The range for optimum results is narrower andfalls within 230% to 250% of the base fabric weight. It is difficult to consistently get into the web with a continuous impregnation process quantities substantially above 250% to 300% of the fabric weight, and, below 200%, the quantity of impregnant is insufficient for general stiffener uses.

The porosity of the dried impregnant depends to a considerable measure upon the solids content ofy the impregnating bath. The solids content should be in theneighborhood of 55% to 65%, and, for optimum results, should be about 60%. If the solids content is higher than 65%, the binder tends to coalesce on the fibers of the base fabric, and the desired porosity is not obtained. If less than 55% of solids are present, it is diflicult to obtain the desired percentage of impregnant in the finished product as discussed above.

By the present invention, it is possible to have a relatively low solids content impregnant and obtain the necessary porosity and distension of the fibers in the napping operation by the use of a thickening agent which is of a thixotropic nature. While the term thixotropic is used in the specification to indicate an increase in the fluidity of the impregnant upon the application of shearing forces, I do not wish'to be limited to the particular theory which thixotropy involves. From actual work, however, it has the impregnant becomes more fluid upon working by the circulating pump diagrammatically shown in the drawing and that the impregnant becomes thicker as the fabric with the impregnant carried on it leaves'the impregnating bath and also apparently increases in thickness upon entrance of the impregnated fabric into the drying oven and upon the application of heat thereto. This may also be termed a desirable consistency and may be said to be determined at least in part by thixotropy, viscous flow, apparent viscosity, etc.

In order to obtain proper distension of the fibers during the napping operation using the equipment referred to above and diagrammatically illustrated in the drawing, the saturant should have a relatively high apparent Viscosity. It is not possible to accurately determine the apparent viscosity of materials such as the impregnant given above, for, as pointed out, it is of a thixotropic nature, and the viscosity changes as the impregnant is subjected to hearing forces, as are necessary in viscosity determinations.

The quantity of thickener employed will depend to some extent at least upon the type of thickener,

weight oftheyresin in ythe mixture, Vthe desired apparent viscosity will be obtained. Such quantities of thickener have no deleterious action on the final stiffener. The waterresistance of the finished product is not materially changed, and the resistance of the material to the absorption of moisture from the atmosphere is not adversely affected. The thickener does have the very salutary effect, however, of providing a porous body of impregnant u on the fibers. Instead of having a continuous film over each of the individual bers,

. the film is discontinuous and porous, the pores being of very small size. Such porosity is not achieved in the absence of the thickener. The thickeners referred to exert their effectsthrough physical action and have no chemical reaction been learned that the nature of the saturating resin solution, the

' weight) is incorporated, based upon theY dry with the resin or other constituents of the saturating solution.

By providing a porous binder for the base fabric, the incorporation of large quantities of filler is made possible. The use of such quantities serves a dual function. In the rst place, the fillers render the product more resistant to change upon the imbibition of moisture from the atmosphere. Stiffener blanks made in accordance with this invention may be readily cut and skived even under relatively high humidity conditions encountered in the summer months in many shoe manufacturing areas. Even more important, however, is the action of the ller as a distender rendering the films of saturant more absorbent upon contact with Water, due to the enormous increase in surface area for contact with moisture.

In the manufacture of the stiifening material, the impregnant is rst prepared by mixing the ingredientsgiven above to form a composition in which the various ingredients are properly mixed and the filler particles are properly dispersed and suspended. This impregnant is deposited in a tank, as shown in the drawing, and a web of base fabric which is preferably a double napped cotton flannel or sheeting weighing approximately 1/2 pound per square yard is fed from a roll into and through the impregnating tank. The speed of movement of the material through the tank is such that the flannel is substantially completely impregnated. As the web is withdrawn from the impregnating bath, it is contacted on its opposite flat faces by a pair of smoothV steel rolls which may be chromium plated. Both of these rolls travel at substantially the same rate of speed and are disposed about 18 inches above the level of the bath of impregnant. As the material is withdrawn from the impregnating bath, the appearance of the sheet changes slightly, indicating that during this int-erval a portion of the water in the saturant is imbibed by the fibrous base fabric and the thickening agent is effective for causing a substantial increase in the apparent viscosity of the impregnating solution which is carried by the base fabric, evidenced by a change in the physical appearance of the surface of the web as it moves from the impregnating solution to the rolls. As the material passes between the rolls, a substantial quantity of the impregnating solution is expressed from the base fabric and the fibers in the flannel are iiuffed up on opposite sides of the sheet, and, due to the apparent viscosity of the impregnant, the napped fibers remain in distended position. I believe that the impregnating solution has some measure of tackiness which causes it to adhere to the smooth napping rolls, and'this tends to distend the bers generally condition, suficient inert thixotropic thickening gel, between about 1% and 5% based on the dry weight of the resin, to cause said resin to dry in discontinuous porous films, and 80% to 120% of finely divided acid-resistant filler based on the dry weight of the resin, said mixture containing between 55% and 65% of solids; (bi) subjecting said impregnated fabric to a napping operation to distend the fibers of the fabric and to meter the quantity of impregnant in and on the fabric to provide a matrix containing when dry between 200% and 300% of the weight of the fabric; (c) heating said mixture on and Within said fabric, while said fibers are maintained in distended condition by the thixotropic action of said gel, until at least about 95% of the moisture is removed from said aqueous mixture and a dried, porous matrix is formed on said distended fibers and within the body of the fabric; and (d) pressing said fabric in such dried condition and while it contains not more than 5% of Water to fracture said porous matrix on said distended fibers and within the body of the fabric at a multiplicity of points throughout its extent to form a stiffener material which may be rendered soft and flaccid substantially instantaneously upon immersion in water.

2. In a method of making a shoe stilener material the steps comprising: (a) impregnating a fibrous base of napped cotton iiannel with an aqueous mixture of a reactive water-soluble ureaiormaldehyde resin stabilized in partially condensed condition, sufficient inert thixotropic thickening gel, between about 1% and 5% based on the dry weight of the resin, to cause said resin to dry in discontinuous porous films, and 80% to 120% of finely divided acid-resistant filler based on the dry weight of the resin, said mixture containing between 55% and 65% of solids; (b) subjecting said impregnated flannel to a napping operation to distend the fibers of the iiannel and to meter the quantity of impregnant in and on the flannel to provide a matrix containing when dry between 200% and 300% of the weight of the flannel; (c) heating said mixture on and within said flannel, while said bers are maintained in distended condition by the thixotropic action of said gel, until at least about 95 of the moisture is removed from said aqueous mixture and a dried, porous matrix is formed on said distended fibers and within the body of the flannel; and (d) calendering said napped flannel in such dried condition and while it contains not more than 5% of water to fracture said porous matrix on said distended bers and within the body of the flannel at a multiplicity of points throughout its extent to form a stiffener material which may be rendered soft and flaccid substantially instantaneously upon immersion in water.

3. In a method of making a shoe stiiener material the steps comprising: impregnating a fibrous base of napped cotton flannel with an aqueous mixture of a reactive water-soluble ureaformaldehyde resin stabilized in partially condensed condition, suicient inert thixotropic thickening gel, between about 1% and 5% based on the dry weight of the resin, to cause said resin to dry in discontinuous porous lms, and to 120% of finely divided acid-resistant filler based on the dry weight of the resin and consisting essentially of talc, said mixture containing between 55% and 65% of solids; (b) subjecting said impregnated flannel to a napping operation to distend the fibers of the flannel and to meter the quantity of impregnant in and o'n the flannel to provide a matrix containing when dry between 200% and 300% of the weight of the flannel; (c) heating said mixture on and within said flannel, while said fibers are maintained in distended condition by the thixotropic action of said gel, until at least about of the moisture is removed from said aqueous mixture and a dried, porous matrix is formed on said distended fibers and within the body of the flannel; and (d) calendering said napped flannel in such dried condition and while it contains not more than 5% of water to fracture said porous matrix on said distended fibers and within the body of the flannel at a multiplicity of points throughout its extent to form a stiffener material which may be rendered soft and iiaccid substantially instantaneously upon immersion in water.

4. A shoe stiifener material made in accordance with the method of claim 1.

5. A shoe stiiener material made in accordance with the method of claim 2.

6. A shoe stiffener material made in accordance with the method of claim 3.

GEORGE E. EIILE.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 1,353,599 Lovell Sept. 21, 1920 1,417,587 Tully May 30, 1922 1,756,010 Boughton Apr. 22, 1930 1,945,449 Redman Jan. 30, 1934 1,984,417 Mark Dec. 18, 1934 2,277,941 Ahny Mar. 31, 1942 2,384,871 Atkinson Sept. 18, 1945 FOREIGN PATENTS Number Country Date 1,219 Great Britain 1869 

1. IN A METHOD OF MAKING A SHOE STIFFENER MATERIAL THE STEPS COMPRISING: (A) IMPREGNATING A FIBROUS BASE OF NAPPED FABRIC WITH AN AQUEOUS MIXTURE OF A REACTIVE WATER-SOLUBLE UREA-FORMALDEHYDE RESIN STABILIZED IN PARTICALLY CONDENSED CONDITION, SUFFICIENT INERT THIXOTROPIC THICKENING GEL, BETWEEN ABOUT 1% AND 5% BASED ON THE DRY WEIGHT OF THE RESIN, TO CAUSE SAID RESIN TO DRY IN DISCONTINUOUS POROUS FILMS, AND 80% TO 120% OF FINELY DIVIDED ACID-RESISTANT FILLER BASED ON THE DRY WEIGHT OF THE RESIN, SAID MIXTURE CONTAINING BETWEEN 55% AND 65% OF SOLIDS; (B) SUBJECTING SAID IMPREGNATED FABRIC TO A NAPPING OPERATION TO DISTEND THE FIBERS OF THE FABRIC AND TO METER THE QUANTITY OF IMPREGNANT IN AND ON THE FABRIC TO PROVIDE A MATRIX CONTAINING WHEN DRY BETWEEN 200% AND 300% OF THE WEIGHT OF THE FABRIC; (C) HEATING SAID MIXTURE ON AND WITHIN SAID FABRIC, WHILE SAID FIBERS ARE MAINTAINED IN DISTENDED CONDITION BY THE THIXOTROPIC ACTION OF SAID GEL, UNTIL AT LEAST ABOUT 95% OF THE MOISTURE IS REMOVED FROM SAID AQUEOUS MIXTURE AND A DRIED, POROUS MATRIX IS FORMED ON SAID DISTENDED FIBERS AND WITHIN THE BODY OF THE FABRIC; AND (D) PRESSING SAID FABRIC IN SUCH DRIED CONDITION AND WHILE IT CONTAINS NOT MORE THAN 5% OF WATER TO FRACTURE SAID POROUS MATRIX ON SAID DISTENDED FIBERS AND WITHIN THE BODY OF THE FABRIC AT A MULTIPLICITY OF POINTS THROUGHOUT ITS EXTENT TO FORM A STIFFENER MATERIAL WHICH MAY BE RENDERED SOFT AND FLACCID SUBSTANTIALLY INSTANTANEOUSLY UPON IMMERSION IN WATER. 